The present invention is directed to improved dihydroxy aluminum sodium carbonate (DASC) compositions, which unlike prior art DASC, form stable, non-gritty suspensions in aqueous solutions. The improved properties of the DASC compositions of the present invention render the compositions particularly useful as components of liquid antacids, and other consumer and industrial products, for which stable, non-gritty suspensions are desirable.
DASC is a known aluminum salt which exhibits excellent acid neutralizing capacity, and therefore is particularly useful in antacid formulations. (See, Grote, U.S. Pat. No. 2,783,179, issued Feb. 26, 1957). However, the use of prior art DASC as the active ingredient in antacid formulations has been generally limited to non-liquid formulations (e.g. Rolaid tablets) because prior art DASC does not form stable aqueous suspensions at concentrations that produce acceptable acid neutralizing capacity. In addition, even dilute suspensions of prior art DASC possess an undesirable gritty appearance and taste, and rapidly form a sediment layer.
Several attempts have been made to stabilize aluminum hydroxide suspensions. For example, Alford, U.S. Pat. No. 2,999,790, issued Sep. 12, 1961, described combining hexitols such as sorbitol and mannitol with aluminum hydroxide gels in water to prevent thickening and hardening of the aluminum hydroxide gels.
Greene, et al., U.S. Pat. No. 3,591,680, issued Jul. 6, 1971, described the use of hydroxypropyl cellulose for stabilizing antacids such as magnesium carbonate, magnesium hydroxide, aluminum hydroxide, or calcium carbonate, which essentially involved slurrying the dry actives with water and hydroxypropyl cellulose.
Schmank, U. S. Pat. No. 3,629,229, issued Dec. 21, 1971, described water soluble antacid formulations that were prepared by reacting aluminum powder or aluminum isopropoxide with polyhydroxyl hydrocarbons.
Rubino, et al., U.S. Pat. No. 4,112,072, issued Sep. 5, 1978, described antacid compositions that were prepared by codrying hydrous, gelatinous aluminum-hydroxide materials with di- or trihydroxy alcohols.
Beekman, U.S. Pat. No. 3,272,704, issued Sep. 13, 1966, described antacid compositions that were prepared by co-drying aluminum hydroxide and magnesium hydroxide gels with hexitols.
Hem, et al., U.S. Pat. No. 3,911,090, issued Oct. 7, 1995, described antacid compositions containing silicate anions and aluminum hydroxy carbonates which purportedly possess the antacid properties of liquid aluminum hydroxide gels.
However, prior to the present invention, no methods have been taught or suggested for preparing DASC compositions which, upon introduction into aqueous solutions, results in suspensions that have the desired properties of stability and non-grittiness.
The present invention is based upon the discovery by the inventors of DASC compositions, which unlike prior art DASC, form stable, non-gritty suspensions in aqueous solutions. The DASC compositions of the present invention, unlike prior art DASC, also can be formulated so that upon introduction into aqueous solutions, the resulting suspensions not only possess the aforementioned desired physical properties, but also have acceptable acid neutralizing capacities. Accordingly, the DASC compositions of the present invention are particularly desirable for use in liquid antacid formulations.
In addition to stability and non-grittiness, the DASC compositions of the present invention also can be formulated to have gelling and/or translucent properties. Accordingly, the DASC compositions of the present invention are also suitable for use as components of other consumer or industrial products such as tooth pastes, soaps, detergents, pharmaceuticals, lotions, nutriceuticals, plastic additives, chemical foaming agents, acid scavengers, gellants, cleaners, and the like, for which stable and non-gritty, and/or gelling and/or translucent properties are desirable.
The properties of the DASC compositions of the present invention relate to the manner in which the compositions are prepared. Specifically, it has been found that if DASC is synthesized under certain temperature conditions, then the resulting dried DASC composition, when reconstituted in an aqueous solution, results in a suspension having the desired properties. It also has been found that if at least one polyol is included in freshly synthesized DASC before drying, or is included during the reaction of DASC, then the resulting co-dried DASC/polyol composition, when reconstituted in an aqueous solution, will also result in a suspension that possesses the desired properties of stability and non-grittiness. In addition, depending upon the choice of polyol, the suspensions also may be prepared to be translucent and/or gelling. Accordingly, in addition to the improved DASC compositions and suspensions containing the same, the present invention also provides processes for preparing the DASC compositions of the present invention.
Additional objects of the invention will be apparent from the description which follows.
The composition of the present invention is directed to a powder that comprises DASC, which upon introduction into an aqueous solution, forms a stable, non-gritty suspension. As used herein, xe2x80x9cstablexe2x80x9d means that the powder does not settle or separate in the suspension but rather stays in solution resulting in a suspension having a homogeneous appearance. This stability lasts for at least three months, preferably at least six months, and most preferably for up to a year or more. xe2x80x9cNon-grittyxe2x80x9d means that the suspension has only minor or no grittiness.
The powder of the present invention also can include at least one polyol. Suitable polyols include but are not limited to sorbitol, glycerin, mannitol, maltodextrin, pentaerythritol, fructose, glucose and sucralose. However, as discussed in the Examples below, the inventors of the present invention have found that polyols such as propylene glycol, 1,3-butylene glycol, neopentyl glycol, polyethylene glycol and sodium carboxymethylcellulose do not result in suspensions having the desired stability and non-gritty properties. Accordingly, such polyols are not included within the term xe2x80x9cpolyolsxe2x80x9d as used herein. The ratio of DASC:polyol to arrive at the desired properties may vary. However, in the preferred embodiment, the weight ratio of DASC:polyol is 0.67:1 to 19:1 (40-95% DASC), and more preferably is 1.5:1 to 5:1 (60-83% DASC).
The DASC powder of the present invention is prepared by reacting an organoaluminum compound with a carbonate in an aqueous solution at a temperature of between about xe2x88x9220xc2x0 C. and about 10xc2x0 C. The weight ratio of organoaluminum compound:carbonate is preferably 1:1 to 1:3. Sodium chloride or isopropyl alcohol also may be added to the reaction mixture. Suitable organoaluminum compounds include aluminum alkoxides such as aluminum iso-propoxide, aluminum ethoxide and aluminum sec-butoxide. Preferably, the organoaluminum compound is aluminum iso-propoxide. The inventors of the present invention have found that the use of aluminum chloride or sodium aluminate does not result in a suspension having the desired properties. Accordingly, aluminum chloride and sodium aluminate are not included within the term xe2x80x9corganoaluminum compoundxe2x80x9d as used herein. The carbonate includes but is not limited to sodium bicarbonate and sodium carbonate, but is preferably sodium bicarbonate.
After the DASC is prepared using the above process, it is isolated by methods known in the art such as filtration, centrifugation, settling, decanting or a combination thereof. For batch preparations, filtration is preferred. The DASC may then be washed with water following isolation to remove isopropyl alcohol formed during the reaction. The isolated DASC is then dried into powder form by suitable methods including but not limited to air-drying, oven-drying, fan-drying, spray-drying or a combination thereof.
When at least one polyol is included in the powder with DASC, it has been found that the desired DASC/polyol powder can be prepared by certain modifications to the above process. Specifically, the polyol(s) can be added directly to the freshly prepared wet DASC before or after the isolation step, or can be combined with the organoaluminum compound and the carbonate reactants before DASC is formed. However, it is preferred that the polyol is added after DASC has been isolated since it has been found that when the polyol is combined with DASC or the reactants before isolation of DASC, some of the polyol may be lost in the isolation step. The inventors also have found that dry DASC cannot be combined with the polyol in water and result in an aqueous DASC/polyol suspension having the desired properties. Accordingly, the use of previously prepared dry DASC is not encompassed by the processes of the present invention.
The organoaluminum compound and carbonate used in preparing the DASC/polyol powder are the same as described above for the DASC powder, with aluminum iso-propoxide and sodium bicarbonate being the preferred reactants. However, the reaction can be performed at a broader temperature of between about xe2x88x9220xc2x0 C. and about 120xc2x0 C. For the sake of ease, the reaction is preferably performed at room temperature. Suitable polyols again include but are not limited to sorbitol, glycerin, mannitol, maltodextrin, pentaerythritol, fructose, glucose and sucralose. However, hexitols such as sorbitol and mannitol are preferred.
The present invention also provides a stable, non-gritty suspension comprising either the DASC powder or the DASC/polyol powder of the present invention. The suspension may be prepared by admixing the powder with an aqueous solution at a w/w that results in the suspension having the desired physical properties. The inventors of the present invention have found that at a w/w of 1-15%, preferably at a w/w of 1-10%, and most preferably at a w/w of 2-6%, the suspension will be stable and non-gritty. However, it is within the confines of the present invention that higher or lower concentrations of the powder may be utilized if they result in a suspension having the desired properties.
The present inventors also have found that the suspensions of the present invention, depending upon the choice and concentration of polyol in the DASC/polyol powder, also possess other desirable properties in addition to stability and non-grittiness. For example, it has been found that the use of sorbitol, glycerin, mannitol, maltodextrin, pentaerythritol and fructose as the polyol can result in a suspension that not only is stable and non-gritty, but also is translucent. As used herein, xe2x80x9ctranslucentxe2x80x9d means that the suspension is not opaque such that light can pass through the suspension in a manner that permits the outline of objects (although not the details of such objects) to be seen through the suspension. In addition, it has been found that the use of polyols such as mannitol or fructose, for example, can result in a suspension that also has gelling properties.
Based upon the aforementioned properties, the powders or suspensions of the present invention are useful as components of various consumer or industrial products for which such properties are desirable. Such products include but are not limited to liquid antacids, tooth pastes, soaps, detergents, pharmaceuticals, lotions, nutriceuticals, plastic additives, chemical foaming agents, acid scavengers, gellants, cleaners, and the like. The formulation of such products with the powders and suspensions of the present invention are well within the purview of those skilled in the art.
However, because the suspensions are stable and non-gritty, and can be formulated to have an acceptable acid neutralizing capacity the suspensions of the present invention are preferably used as the active ingredient in liquid antacid formulations. In this connection, it is preferred that the suspensions of the present invention have an acid neutralizing capacity (ANC) of 0.1-3.0, and more preferably an ANC of 0.5-1.0. However, higher or lower ANC values can be obtained if desired. The ANC can be determined using the procedures outlined in the U.S. Pharmacopoeia. In addition to the stability and non-gritty properties, the antacids can also be formulated to have gelling and/or translucent properties, as described above. In the particularly preferred embodiment, the liquid antacids are translucent, stable, non-gritty and non-gelling. Liquid antacids having these properties can be prepared as described in the examples below using polyols such as such sorbitol, glycerin, mannitol, maltodextrin, pentaerythritol and fructose. Finally, it is within the confines of the present invention that the liquid antacid formulations may be combined with flavoring agents, coloring agents, preservatives, and the like, if so desired.